Short answer: far longer than the simple math suggests — because a fridge's compressor cycles on and off. Here's the real-world runtime by power station size.
A full-size refrigerator draws about 150 running watts, but it isn't running constantly — the compressor kicks on and off, averaging roughly 50–70 watts over an hour. That's why a fridge lasts much longer than "capacity ÷ 150W" implies. The table shows both figures (assuming ~85% usable capacity):
| Power station | Usable energy | If running flat-out (150W) | Real-world (cycling) |
|---|---|---|---|
| 300 Wh | ~255 Wh | ~1.7 hours | ~4–5 hours |
| 500 Wh | ~425 Wh | ~2.8 hours | ~7–9 hours |
| 1000 Wh | ~850 Wh | ~5.7 hours | ~12–17 hours |
| 2000 Wh | ~1700 Wh | ~11 hours | ~1–1.5 days |
| 3600 Wh | ~3060 Wh | ~20 hours | ~2–2.5 days |
Mini-fridges (~100W, lower average draw) last roughly 50% longer than the figures above. Older or garage fridges in hot conditions run more often and last less.
For outage backup of a fridge for a full day, get 2000Wh with an output above the fridge's surge (often 600–800W). Add a solar panel and you can run it indefinitely. For occasional short outages, 1000Wh is a sensible minimum.
See 2000Wh options →Want to factor in your other appliances too (lights, internet, phones)? Use the full power station size calculator — it adds everything up and handles surge automatically.
Roughly 12–17 hours in real-world use (the fridge cycles, averaging ~50–70W). The flat-out figure at 150W is ~5–6 hours.
Aim for 1000–2000Wh and an output above the fridge's startup surge (600–800W). 2000Wh usually covers a fridge for more than a day, and pairs well with solar.
It can — a fridge can spike to 2–3× its running watts at startup. Make sure the output/inverter rating is above that surge, not just the capacity.